setting up mass subdomains and have immediate access to them

[Kevin Darcy]

kumsanto wrote:
> Does anyone know how for the scenarios of  blogspot or wordpress or
> meetup subdomain URLs are generated immediately after user sign up. I
> tried to follow methods mentioned in apache documentation
> (http://httpd.apache.org/docs/1.3/vhosts/mass.html) and those things
> work but it takes a while before those subdomains are visible from
> remote computers.. i.e. after I set up user1.xxx.com and user2.xxx.com
> , if user visits these URLs immediately there is no page available but
> after some time these domains are available.. Any clues? Suggestions?
>   
You might be running into a negative caching problem. If the parent 
domain has negative caching set to an hour, say, and a client queries 
the subdomain through an intermediary resolver just before it exists, 
then the NXDOMAIN that is returned may be cached by the intermediary 
resolver and it could be almost an hour before subdomain is visible to 
the client.

You can "solve" this by lowering the negative caching TTL, of course, 
but that's a rather anti-social way to go about it, since it makes 
everyone else's nameservers work harder for regular resolution of 
regular names in your parent domain. It's really not a scalable solution 
to the "problem" that you're trying to solve.

What I think some folks do is have a wildcard A record in the parent 
domain pointing to a web server that has the content of the new website 
(or does an HTTP-level redirect, using some established name, to a site 
that has the new content), until the DNS has enough time to propagate 
and/or the negative cache entries have enough time to expire.

                                                                         
                              - Kevin